In situ experiments of graphite intercalation with potassium have been performed under high vacuum (HV) conditions. A detailed Raman lineshape analysis of the G‐line was applied to determine the intrinsic response of the stage one KC8 compound. Four defect‐modulated graphite single crystals were analyzed. We observe five vibrational modes (∼560, 1260, 1510, 1547, and 1563 cm−1). From a Breit–Wigner–Fano (BWF) lineshape analysis we elucidate the contribution of each vibrational mode observed. The intensity of the z‐axis mode (CZ) around ∼560 cm−1 varies depending on the defect modulated nominal KC8 crystal chosen. We prove that the intrinsic G‐line of KC8 is at 1510 cm−1, and it is strongly dependent on the actual defect content in the sample, which has important implications for the electron phonon coupling (EPC) responsible of superconductivity in this system. 相似文献
Collective excitations and their coupling to optical phonons have been studied for a two-dimensional electron gas in
-doped polar semiconductors within the random-phase approximation. The inelastic light scattering spectrum due to the coupled plasmon–phonon modes are calculated for the multisubband two-dimensional electron systems. Our calculation shows that, due to the high electron density in these systems, both intrasubband and intersubband plasmons are strongly coupled to the optical-phonons. On the other hand, due to the high impurity concentration, level broadening modifies the inelastic light scattering spectrum significantly. 相似文献
The effect of Pr doping on structural properties and room temperature Raman spectroscopy measurements is investigated in manganites (Eu1−xPrx)0.6Sr0.4MnO3 (0≤x≤1.0) with fixed carrier concentration. The result of the Rietveld refinement of x-ray powder diffraction shows that these compounds crystallize in an orthorhombic distorted structure with a space group Pnma. It is evident that, with increasing Pr substitution, three types of orthorhombic structures can be distinguished. The phonon frequencies of the three main peaks, in room temperature Raman-scattering measurements, have been discussed together with their structural characteristics, such as bond-length, bond-angles, and the change of orthorhombic structure type. With the increase of Pr content, the mode at 491 cm−1 also shows a corresponding change. A step effect becomes evident, which seems to indicate the close dependence between the frequency shift of this mode and the change in crystal symmetry. This further supports the notion that the mode at 491 cm−1 is closely correlated with the Jahn–Teller distortion. Moreover, we have found that the lowest frequency peak (assigned as an A1g phonon mode) depends linearly on the tolerance factor t. 相似文献
Efficient high‐gain many‐phonon steady‐state stimulated Raman scattering (SRS) was excited in the novel χ(3)‐active organic crystal of di‐glycine nitrate (DGN), (NH2CH2COOH)2 · HNO3, at room temperature under picosecond laser pumping in the visible and near‐IR regions. Besides high‐order Stokes and anti‐Stokes (comb) generation in this centrosymmetric crystal, several cascaded and cross‐cascaded χ(3) ↔ χ(3) nonlinear photon–phonon interactions were observed. The recorded Raman‐induced lasing wavelengths were identified and attributed to the SRS‐promoting optical vibration modes ωSRS1 ≈ 1058 cm−1, ωSRS2 ≈ 2985 cm−1, ωSRS3 ≈ 895 cm−1, and ωSRS4 ≈ 3000 cm−1. The measured large Raman frequency shifts (≈3000 cm−1) and estimated moderately high steady‐state Raman gain coefficients ( ≥ 6.5 cm · GW−1) make this DGN crystal attractive for a number of new applications in modern laser physics and nonlinear optics. 相似文献
The possibility of multiferroicity arising from charge ordering in LuFe2O4 and structurally related rare earth ferrites is reviewed. Recent experimental work on macroscopic indications of ferroelectricity and microscopic determination of coupled spin and charge order indicates that this scenario does not hold. Understanding the origin of the experimentally observed charge and spin order will require further theoretical work. Other aspects of recent research in these materials, such as geometrical frustration effects, possible electric‐field‐induced transitions, or orbital order are also briefly treated.
Non‐reciprocal devices serving as fundamental elements in photonic and microwave circuits have attracted great attention for its applications in both classical and quantum information processing. The spin–orbit coupling (SOC) of light in microstructures shows that the polarization affects and controls the spatial degrees of freedom of light, which could been exploited to break the reciprocity of light transmission. Here, non‐reciprocal light transmission is demonstrated experimentally in high‐quality factor yttrium iron garnet microspheres via photonic SOC and Faraday effect. By applying an magnetic field in the vertical direction of resonator equator, the degeneracy of the clockwise and counter‐clockwise whispering gallery modes are lifted. The non‐reciprocal effect is shown for both polarizations and promises applications including non‐reciprocal photonic devices, magneto‐optic modulators, and magnetometers. 相似文献
